According to Penn Jillette on his podcast Penn's Sunday School (episode 406, June 24, 2018) the part of Marty Crane was specifically written for him, but he angered someone on the production team with some political humor. So they fired him. Now having some free time on his schedule, he contacted the producers of Lois & Clark: The New Adventures of Superman (1993) and they offered him a part instead. (see Illusions of Grandeur (1994)).